Bimetal strip thermostat



Dec. 16, 1952 C. L. HILTENBRAND BI METAL ST RIP THERMOSTAT Filed March 18, 1950 3 Sheets-Sheet l MM 524M 630. MM

Filed March 18. 1950 1952 c. L. HILTENBRAND ,171

BIMETAL STRIP THERMOSTAT 3 Sheets-Sheet 2 F4: j //l j Dec. 16, 1952 C. L. HILTENBRAND BIMETAL STRIP THERMOSTAT 3 Sheets-Sheet 3 Filed March 18, 1950 Patented Dec. 16, 1952 BIMETAL STRIP THERMOSTAT.

Charles Lon Hiltenbrand, Neuilly-sur-Seine, France, assignor to Perma, Paris, France, a

French company Appiication March 18, 1950, Serial No. 150,394 In France March 23, 1949 1 Claim.

The present invention has for its object a bimetalstrip thermostat for use in controlling the operation of electric heating elements.

The device accordingto the invention is characterized thereby that th bimetallic strip is provided at one end thereof with a fork mounted for rocking motion about a fixed pivot pin, while its other end engages a push piece the displacements of which result in the opening or the closing of the circuit through which the heating element is supplied with current, the deformation of the bimetallic strip by the action of the heat being such that the latter will com into engagement midway of its ends with the heating element, while that end thereof which is remote from the fork will displace the push piece in a direction corresponding to the opening of the heating element current supply circuit.

For instance, a thermostat according to the invention comprises a frame, a pivot pin carried by said frame, a bimetallic strip provided at the one end thereof with a yoke pivoted on said pin, a-supporting member likewise provided with a fork pivoted on said pin and on which a pair of flexible metal strips are secured at their one ends through the medium of insulators, while the other ends of said strips carry ach a contact stud belonging to an electric circuit and urged into engagement with each other due to the flexible character of the strips, a push piece carried by that flexible strip which is remote from the bimetallic strip and adapted when acted upon by that end of th latter which is r emote from the pivot pin to disengage the contact studs from each other, the heating element being switched into or out of operation depending on whether the said electric circuit is closed or opened.

One embodiment of the invention will be described hereinafter for the purpose of exemplification, reference being had to the appended drawings in which:

Figure 1 is an isometric perspective view of the thermostatic device of which the frame and the supporting member are partly broken away.

Figures 2 and 3 are diagrammatic vertical sections of the device in two different positions corresponding respectively to the closed and the open condition of the heating element supply circuit.

The heating element which the thermostatic device is intended to regulate and control consists e. g. of a metal tube in which an electric resistance is enclosed. Said tube is shown in dotted lines in the figures.

The device comprises a frame I which rests on the heating element 2. A bimetallicstrip 3' arranged in close relation to the tubular element 2 is provided at the one end thereof with a fork 4 mounted for rocking motion on a pin 5. A sup-porting member 6 is likewise provided with a fork 1 pivoted on pin 5'. Each of a pair of flexible strips 8, 9 is secured at the one end thereof to member 6 by means of rivets Ill and carries a contact stud If at its opposite end. In addition, the strip 9 carries a push piece 12 in the lower end of which rests on the end ll of the bimetallic strip 3.

The strips 8 and 9 are insulated from the supporting member 6 by means of a non-conductive material l3 and belong to an electric circuit [4 which is closed when the contacts H are in-engagement with each other.

The bimetallic strip initially occupies the position shown in Fig. 2; as its temperature rises it undergoes adeformation (see Fig. 3) and its middle portion [5 comes into engagement with the tubular element 2, while its end I'I lifts the push 12, which results in the disengagement of the contact studs H and consequently in th opening of the electric circuit l4.

Conversely, as the bimetallic strip cools, it resumes again its straight position shown in Fig. 2, while owing to the resiliency of strip 9 contact is reestablished at studs II and the electric circuit I4 is once more closed.

The closing and opening of the said electric circuit are caused either directly or through the medium of relays to effect the closing and opening of the circuit that contains the heating resistance within the tubular element 2.

The device can be set easily by means of a screw l8 the tip of which engages that end of member 6 which is remote from fork I. Effectively, the position of the tip of screw l8 determines the extent to which the bimetallic strip must deform to cause the opening of the circuit M. In fact, the bimetallic strip 3 is shown in Fig. 2 as if it were parallel to the heating element 2. But even if it is supposed that the assembly formed by the strips 3, 6, 8, 9, is lowered about the pin 5 until the free end of strip 3 comes into contact with the element 2, the electric circuit will be opened only when the strip 3 will be deformed sufiiciently to raise the members 6, 8, 9, until the member 6 comes into contact with the screw l8, and then any additional upward movement of strip 3 will separate the contact piece ll carried on the strip 9 from the contact piece ll carried on the strip 8. The de- 3 vice can thus be set to open the circuit at any desired temperature.

The thermostatic device may operate in the same manner if it is turned upside down, with the heating element 2 above the bimetallic strip 3. The operation is also the same when the device is placed in a vertical or in any inclined position.

The essential advantages of the device are as follows:

The transmission of the heat from the heating element to the bimetallic strip is almost instantaneous.

The regulating process is accelerated due to the fact that the strip moves towards the heat source as the temperature rises and away therefrom as it descreases.

Responsivity and consequently sensitiveness are maximum in the neighbourhood of the desired temperature.

Adjustment is very easy since the point at which the studs will lose contact with each other in dependency on the deformation of the bimetallic strip and consequently on the temperature is modified with maximum progressiveness owing to the position of the screw [8.

The whole structure is sturdy since the parts of the mechanism are assembled positively without the interposition of insulators.

One single pivot pin is provided, and the play of the forks mounted thereon is consistent with an accurate working.

Last, the bimetallic strip is free and no other operation has to be performed thereon than cutting it to size and spot-welding it to its fork, which excludes any risk of instability ascribable to internal stresses set up in the course of its manufacture.

It is to be understood that the embodiment of the invention described in connection with the appended drawing is given merely by way of example and that many modifications may be made in the details thereof without thereby departing from the general principle of the invention.

What I claim as new is:

A thermostatic device for controlling the operation of an electrically heating element comprising a frame adapted to be disposed against said heating element, a pivot pin fixed on said frame at a certain distance from said heating element, a bimetallic strip hingedly mounted on said pivot pin end disposed in the vicinity of said heating element and adapted to be deflected under the infiuence of heat emitted from said heating element so that the higher the temperature the nearer will said bimetallic strip be in relation to said heating element, a supporting member pivoted on said pivot pin, a pair of resilient metal strips having their one ends fast with but electricaliy insulated from said supporting member, a contact stud on the opposite end of each of said resilient metal strips, said contact studs engaging each other when the thermostatic device is inoperative, a push member having one end carried by the resilient metal strip which is farthermost from said bimetallic strip and its other end registering with the free end of said bimetallic strip, and therefore adapted to cooperate with said free end so as to be pushed thereby when said bimetalic strip, already deflected by the influence of heat radiated by said heating element, bears with the top portion of its curvature against said heating element.

CHARLES LEON HILTENBRAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,415,050 Reichart May 9, 1922 1,798,854 Satchwell Mar. 31, 1931 2,008,163 Walder July 16, 1935 2,267,387 Winborne Dec. 23, 1941 2,248,676 Jensen July 8, 1944 2,452,508 Ulanet Oct. 26, 1948 2,518,595 Bletz Aug. 15, 1950 

